/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.monitoring;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.hadoop.hbase.util.GsonUtil;
import org.apache.hadoop.util.StringUtils;
import org.apache.yetus.audience.InterfaceAudience;

import org.apache.hbase.thirdparty.com.google.gson.Gson;

@InterfaceAudience.Private
class MonitoredTaskImpl implements MonitoredTask {
    private long startTime;
    private long statusTime;
    private long stateTime;
    private long warnTime;

    private volatile String status;
    private volatile String description;

    protected volatile State state = State.RUNNING;

    private boolean journalEnabled = false;
    private List<StatusJournalEntry> journal;

    private static final Gson GSON = GsonUtil.createGson().create();

    public MonitoredTaskImpl() {
        startTime = System.currentTimeMillis();
        statusTime = startTime;
        stateTime = startTime;
        warnTime = startTime;
    }

    private static class StatusJournalEntryImpl implements StatusJournalEntry {
        private long statusTime;
        private String status;

        public StatusJournalEntryImpl(String status, long statusTime) {
            this.status = status;
            this.statusTime = statusTime;
        }

        @Override
        public String getStatus() {
            return status;
        }

        @Override
        public long getTimeStamp() {
            return statusTime;
        }

        @Override
        public String toString() {
            StringBuilder sb = new StringBuilder();
            sb.append(status);
            sb.append(" at ");
            sb.append(statusTime);
            return sb.toString();
        }
    }

    @Override
    public synchronized MonitoredTaskImpl clone() {
        try {
            return (MonitoredTaskImpl) super.clone();
        } catch(CloneNotSupportedException e) {
            throw new AssertionError(); // Won't happen
        }
    }

    @Override
    public long getStartTime() {
        return startTime;
    }

    @Override
    public String getDescription() {
        return description;
    }

    @Override
    public String getStatus() {
        return status;
    }

    @Override
    public long getStatusTime() {
        return statusTime;
    }

    @Override
    public State getState() {
        return state;
    }

    @Override
    public long getStateTime() {
        return stateTime;
    }

    @Override
    public long getWarnTime() {
        return warnTime;
    }

    @Override
    public long getCompletionTimestamp() {
        if(state == State.COMPLETE || state == State.ABORTED) {
            return stateTime;
        }
        return -1;
    }

    @Override
    public void markComplete(String status) {
        setState(State.COMPLETE);
        setStatus(status);
    }

    @Override
    public void pause(String msg) {
        setState(State.WAITING);
        setStatus(msg);
    }

    @Override
    public void resume(String msg) {
        setState(State.RUNNING);
        setStatus(msg);
    }

    @Override
    public void abort(String msg) {
        setStatus(msg);
        setState(State.ABORTED);
    }

    @Override
    public void setStatus(String status) {
        this.status = status;
        statusTime = System.currentTimeMillis();
        if(journalEnabled) {
            journal.add(new StatusJournalEntryImpl(this.status, statusTime));
        }
    }

    protected void setState(State state) {
        this.state = state;
        stateTime = System.currentTimeMillis();
    }

    @Override
    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public void setWarnTime(long t) {
        this.warnTime = t;
    }

    @Override
    public void cleanup() {
        if(state == State.RUNNING) {
            setState(State.ABORTED);
        }
    }

    /**
     * Force the completion timestamp backwards so that
     * it expires now.
     */
    @Override
    public void expireNow() {
        stateTime -= 180 * 1000;
    }

    @Override
    public Map<String, Object> toMap() {
        Map<String, Object> map = new HashMap<>();
        map.put("description", getDescription());
        map.put("status", getStatus());
        map.put("state", getState());
        map.put("starttimems", getStartTime());
        map.put("statustimems", getCompletionTimestamp());
        map.put("statetimems", getCompletionTimestamp());
        return map;
    }

    @Override
    public String toJSON() throws IOException {
        return GSON.toJson(toMap());
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder(512);
        sb.append(getDescription());
        sb.append(": status=");
        sb.append(getStatus());
        sb.append(", state=");
        sb.append(getState());
        sb.append(", startTime=");
        sb.append(getStartTime());
        sb.append(", completionTime=");
        sb.append(getCompletionTimestamp());
        return sb.toString();
    }

    /**
     * Returns the status journal. This implementation of status journal is not thread-safe. Currently
     * we use this to track various stages of flushes and compactions where we can use this/pretty
     * print for post task analysis, by which time we are already done changing states (writing to
     * journal)
     */
    @Override
    public List<StatusJournalEntry> getStatusJournal() {
        if(journal == null) {
            return Collections.emptyList();
        } else {
            return Collections.unmodifiableList(journal);
        }
    }

    /**
     * Enables journaling of this monitored task, the first invocation will lazily initialize the
     * journal. The journal implementation itself and this method are not thread safe
     */
    @Override
    public void enableStatusJournal(boolean includeCurrentStatus) {
        if(journalEnabled && journal != null) {
            return;
        }
        journalEnabled = true;
        if(journal == null) {
            journal = new ArrayList<StatusJournalEntry>();
        }
        if(includeCurrentStatus) {
            journal.add(new StatusJournalEntryImpl(status, statusTime));
        }
    }

    @Override
    public void disableStatusJournal() {
        journalEnabled = false;
    }

    @Override
    public String prettyPrintJournal() {
        return StringUtils.join("\n\t", getStatusJournal());
    }

}
